Pneumonia is the leading cause of child death worldwide. Data from Bangladesh indicates that influenza has a substantial association with pneumonia among children less than two years old. This study will use commercially available trivalent inactivated vaccine (killed vaccine) to see if it can prevent early childhood pneumonia among children less than two years old. The study will vaccinate children across three seasons (3 years), and look at the effect on the attack rate of pneumonia, as well as its effects on laboratory-confirmed influenza. It will also look at the effect on laboratory-confirmed influenza illness among the non-vaccinated household contacts of all ages of these children.